1. Field of Invention
The invention relates to a fuel cell output characteristic estimation apparatus and an output characteristic estimation method, a fuel cell system and a vehicle having the same, and a fuel cell output control method and a data storage medium that stores a program to implement the method. More particularly, the invention relates to an output characteristic estimation apparatus that estimates an output characteristic of a fuel cell and an output characteristic estimation method for estimating an output characteristic of a fuel cell, a fuel cell system having a fuel cell and a vehicle having the fuel cell system, and a fuel cell output control method for controlling an output of the fuel cell and a data storage medium that stores a computer-readable program that causes a computer to function as a fuel cell output characteristic arithmetic unit and/or a control unit for the fuel cell system.
2. Description of Related Art
There has been proposed a fuel cell system provided with a commercial power supply or other power generating device that supplies electric power to and receives the electric power from the fuel cell in case of short or excessive supply of the output generated by the fuel cell (see, for example, JP-A-3-80316). In this system, when a power consumption of a load is within a predetermined range of the power that can be supplied by the fuel cell, all the power consumption of the load is covered by the power generated by the fuel cell. When the power consumption of the load exceeds the predetermined range, the excessive part of the power requirement is covered by a DC power obtained by rectifying the power supplied by a commercial power supply or other power generating device. As a result, the fuel cell is ensured to be effectively used.
In the aforementioned type of the fuel cell system, however, owing to a change in the output characteristic of the fuel cell as it has been used for an extended period of time, it may happen that the entire power consumption of the load cannot be covered by the fuel cell even when it is determined that the power consumption of the load is within the predetermined range of the power supplied by the fuel cell. An energy efficiency of the fuel cell also changes at different operation points depending on an output characteristic. Therefore, the output characteristic has to be taken into account when an overall energy efficiency of the entire system is considered.
The applicant of the invention has proposed a system that determines a fuel cell output by taking account of the output characteristic of the fuel cell for the purpose of enhancing an energy efficiency of the fuel cell system (see JP-A-2000-12059).